The present invention relates to a power semiconductor device, and more particularly, to a structure and method for forming a power semiconductor device including a guard ring region to protect a control device.
In semiconductor integrated circuit (IC) having a plurality of devices monolithically integrated in a single semiconductor substrate, unwanted parasitic elements such as transistors, diodes, or resistors, may cause problems such as cross-talk or latch-up. Where power semiconductor devices are monolithically integrated in a p-type semiconductor substrate, a parasitic PNP bipolar transistor may be formed by the p-type semiconductor substrate, an n-type layer and a p-type region in the n-type layer. The parasitic PNP bipolar transistor may be turned on when one of the PN junctions of the bipolar transistor is forward-biased, and may cause latch-up or permanent damage to the device. Also, leakage currents, including current caused by the parasitic PNP bipolar transistor, may increase the potential of the p-type region due to resistivity of the p-type region, thereby turning other parasitic NPN bipolar transistors on.
An example of the above semiconductor circuit is a power semiconductor device in which a high-power driving device for driving a power element such as a motor, and a low-power control device for controlling the high-power driving device are integrated in a single semiconductor substrate. Such semiconductor device is also referred to as a smart integrated circuit, and provides advantages of superior performance, cost-saving, and improvement in the reliability of the device. In such smart integrated circuit, conditions for generating a forward voltage turning on a parasitic element often arise due to instantaneous voltages induced during switching an inductive power element such as a motor. As indicated above, when these parasitic elements are turned on, latch-up or other undesirable problems can occur. Therefore, there is a need for techniques that address problems caused by such parasitic elements.